1. Field of the Invention
The invention relates to a method as well as to a system Particularly for the operation of high-speed plants for slabs and, in this connection, particularly in combination with rolling mills, it is important to be able to operate the continuous casting plant at a high and controlled speed in a safe way.
This necessity of safety for casting particularly at high casting speeds up to 10 m/min. makes it necessary to carry out control of numerous processing data, which are intermeshed in a complex fashion with one another, by means of automation.
This automation must be reduced with respect to its external operation language to a simple functional language which is easily manageable by the operating personnel.
Moreover, the degree of automation, which in regard to its operating language knows only the selection of casting speed and the control all of the narrow side heat flow at the operator (NO) or drive (ND) side, should provide the possibility of operation by autopilot when certain conditions such as
a controlled steel temperature in the distributor
a good oxidic purity of the steel
a calm meniscus as well as
a constant and uniform heat flow of the faces are present.
2. Description of Related Art
The prior art discloses the measuring of the heat flows of all four copper plates of a slab casting mold (DE 4117073) but in this patent document no prior art as a function of the casting speed is disclosed. For example, a speed increase has a minimal effect on the casting mold stress, expressed as MW/m2, and a great effect on the strand shell stress expressed as MWh/m2.
FIG. 1 shows this correlation and illustrates that at high casting speeds, when using casting powder and a certain castings speed of, for example,  greater than 4.5 m/min., the casting mold stress remains almost constant and the strand shell stress is greatly reduced. The reason for this is that at high casting speed a constant slag film and thus a constant heat transfer occurs but a residence time of the strand shell within the casting mold decreases proportionally to the casting speed increase. This illustration makes clear that with increasing casting speed the casting mold stress no longer increases and the casting shell stress decreases so that the risk of fracture formation is reduced but also the casting shell becomes thinner and hotter, for example, at the end of the casting mold.
In FIG. 2, the interrelationships are represented between
casting slag film,
the strand shell temperature, for example, at the exit of the
casting mold, strand shell thickness, and shrinkage,
casting mold and strand shell stresses or shrinkage,
maximum casting mold skin temperature at the meniscus and thus of the casting mold service life in relation to the recrystallization temperature which results in softening of the cold-rolled copper.
U.S. Pat. No. 3,478,808 discloses a method for controlling the parameters of a continuous casting plant for casting steel. Nominal values of parameters, which have been taken from a previous casting process, are stored; actual values of the parameters are recorded, an adjustment of the actual and nominal values is carried out, and a control of the parameters is performed. The disclosed parameters are inter alia the flow speed, the heat removal rate within the casting mold and the removal speed.
Based on this, it is an object of the invention to further develop a method and a system for performing the method for a controlled operation of a continuous casting plant for casting slab, in particular, thin slab, with very high casting speeds.
An automation of the continuous casting process based on an xe2x80x9conlinexe2x80x9d data acquisition is made possible which enables in addition to
a semi-automation, i.e., the control of the narrow side conicity and the casting speed, also
a full automation in the sense of an autopilot operation with consideration and as a function of the steel temperature in the distributor and with the prerequisite of a controlled
purity,
meniscus, and
face heat flow.
This object is solved by the features of the method claim 1 and the device claim with their dependent claims for configuring the invention.